Male, green eyes. His hair is a bit rougher than Kusuri's, though the style is the same. He always looks angry and acts just as grumpy. He insists he won't give his daughter to a 'pest' like Rentaro (though Rentaro is relentless). When the transformation wears off, he becomes incredibly muscular (x100) with a terrifying expression, yet he still can't win against his wife.

Female, turquoise eyes. Her hair is softer than Kusuri's, though the style is the same. She is pure, kind, and the epitome of a gentle mother. She is so positive that she even thinks she'd want to date Rentaro if they were the same age. Her original form is a classic motherly beauty, and she possesses the incredible ability to calm the father down.

Female, turquoise eyes. She has long red hair and sparkling green eyes. It's hard to believe she's in her 80s. She has a wild past, having served on emergency missions during the war. (Spoiler: She becomes Rentaro's next girlfriend). She is kind and acts like a true grandmother. Because the drug's effect was so strong, modern medicine cannot return her to her original form, but she remains positive about it.

Female, emerald eyes. Rentaro's girlfriend with spiky red short hair and an ahoge. She has turned into an 8-year-old due to the drug's effects. A mad scientist who is obsessed with drugs. A genius who was holding medicine bottles at 100 days old and creating drugs by 8 months. She speaks with the verbal tic '~nanoda!' or '~da!'. In her original form, she is a young woman and Rentaro's senior (18 years old).